Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Rank modulation is a scheme that uses the relative order of cell levels to represent data. Rank modulation may be implemented in flash memories, phase-change memories, and other circuits. A challenge with rank modulation for multilevel flash memory is that to be competitive with standard multilevel flash memories, large number of cells may need to be grouped into sets and ranked together. For example to replace a 3 bit/cell NAND flash memory in terms of storage density, sets of 20 cells or more may have to be used. To rank N cells, a conventional algorithm may include approximately N iterations. In each iteration, ranking circuitry may compare a level of all the cells within a set simultaneously and indicate which one has the highest level. Thus, the relatively slow reading (or ranking) process for ranking modulation based flash memory may be an impediment to its implementation.